Hard alloys



Patented Jan. 25, 1938 PATENT OFFICE HARD ALLors Clarence W. Balke, Highland Park, Ill., assignor to Ramet Corporation oi America, North Chicago, 111., a corporation of Illinois No Drawing.

Application March I, 1932,

Serial No. 597,416

5 Claims.

This invention relates in general to hard alloys, and has more particular reference to an alloy of tantalum carbid, tungsten, and nickel.

The invention includes among its objects the 5 provision of a hard and tough alloy suitable for use in the fabrication of metal working tools consisting substantially entirely of tantalum carbide, but including in addition thereto, tungsten and nickel making up together not more than twenty-five per cent of the alloy, and the provision of such an alloy which has an actual density greater than the mean or average density of its constituents, and which, when in the form of metal working tools, even when used in the work- '15 ing or cutting of steel and like materials at I prefer to make the tantalum carbide by heat- 3o ing a mixture of finely divided tantalum and carbon in hydrogen or in vacuo, to about 2000" C. in order to form tantalum carbide according to the formula TaC, having substantially 6.2% carbon, and in order to prevent embrittling gases 35 or substances such, for example, as oxygen, from contaminating the carbide.

This*tantalum carbide is then reduced to a finely divided form and finely divided tungsten in the desired proportions is admixed therewith.

40 To this mixture of tantalum carbide and tungsten, such an amount of nickel is added that the total tungsten nickel content will not exceed 25% by weight of the entire alloy, the percentage by weight of nickel being greater than the 45 percentage by weight of tungsten. This mixture is brought to a desired size and shape and subsequently heat treated in vacuo. The nickel is preferably added by grinding the other constituents by means of nickel grinders in the pres- 50 ence of a low boiling point hydro-carbon, such as naphtha, which may be subsequently volatilized out by heat in order to prevent contamination by embrittling gases.

For the best results, the heat treatment in Y 55 vacuo of the mixed powders which have previously been formed as by pressing to a desired size and shape, should be carefully carried out in order to produce a material which upon cooling will have a greater density than the mean or average density of the tantalum carbide, tung- 5 sten, and the nickel. Of course, the exact temperature to which the pressed powders will be heated may vary slightly in accordance with the formula being employed in the formation of the alloy. I have found, however, that the temperature should not exceed that minimum temperature at which maximum shrinkage of the powdered mixture occurs. This temperature may readily be determined by trial or experiment for any proportion of constituents. For exam- 16 ple, I have found that for a mixtureof substantially 80% by weight of tantalum carbide powder, 9% by weight of tungsten powder, and 11% by weight of nickel powder, the final heat treating step in vacuo should not exceed 1400 C..and 20 1 preferably should be about 1380 C.

In so heating the pressed powders in vacuo, the relatively great shrinkage of the pressed mixture apparently takes place substantially entirely during a relatively small change in temperature near the final or'desired temperature.

It is important that this shrinkageoccurs or takes place graduallylf the maximumbenefits of this invention are to be attained. Accordingly, I bring the pressed powdersup to a temperature of about 1100 C. and thereafter slowly increase this temperature during from about one and one-half to about two hours to the final temperature of about 1380 C. whereby to control for the most part, the relatively great shrinkage 5 of the pressed powders.

This novel alloy of mine at a magnification of 1500 diameters is substantially free of porosity and has a material or an alloy which resembles in the microphotographs, crystallites intermit- 40 tently but uniformly dispersed throughout a substantially aphanitic' structure or phase, or at least a phase that has such exceedingly fine grains that they are not discernible. This intermittent material is rich in nickel and probably includes some or all of the tungsten and some of the tantalum carbide which may be dissolved in the nickel-rich alloy.

My novel alloy is remarkably hard, strong, and tough, the Rockwell A hardness with a 60 kilogram load on the C scale ranging between 8'7 and 91. The Brinell strength of a piece of my alloy inch by V inch, measured between supports 1; inch apart is between 2300 and 2600.

I have found that the chips from the work,

when my tool is employed for working or cutting, for example steel or steel alloys, at a speed of say 125 feet per minute or more, do not stick to the tool and take with them, when subsequently dislodged, small particles of the tool material, or do not wear away or crater the tool, thereby weakening the working edge by robbing it of support material. In this manner frequent regrinding and frequent failures caused by cratering or wearing of the tool as described, are avoided.

My alloy is substantially inert chemically to substances or compounds which are commonly used as coolants, such as lactic acid. In fact, chemicals which ordinarily attack some of the constituents, such as nitric acid and sodium hydroxide, seem to have, very little or no effect upon my alloy.

Illustrative of the tenacity or toughness of the cutting edge or working portion of tools fabricated from my novel alloy, I.have found that a 5 inch milling cutter having ten blades composed of the alloyof this invention may be employed to face off a 4 inch by 12 inch block of B. A. E. steel 1020 taking a cut inch deep at a carriage or table speed of 32 inches per minute and a cutting speed of 232 R. P. M. without cratering and without showing a relatively rapid increase in horse power consumption in successive cuts. The horse power consumption for various cuts made as just described, are given by way of example below in order to show the durability or tenacity of the cutting edge of such tools.

Horsepower H. P. consumption on first cut 9.38 H. P. consumption on th out 14.08

Thus an alloy having the desirable properties of great hardness and strength, durability and chemical inertness, is provided and may be readily fabricated as working portions which may readily be attached to body or shank portions to provide tools that resist cratering and do not require frequent regrinding or replacement.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. A method of making a tool alloy having a greater actual density than the average density of its constituents, which comprises heating a mixture including tantalum carbide, nickel, and tungsten powders to a temperature at which appreciable shrinkage begins in vacuo, and thereafter slowly raising the temperature of said mixture in vacuo to 1380 0., whereby to control the shrinkage of the mixture.

2. A method of making a tantalum carbide alloy including up to 25% by weight of nickel and tungsten, which comprises heating the mixture in vacuo to about 1100 C. and slowly raising the temperature of said mixture in vacuo from 1100 to 1380 6., whereby the nickel and tungsten are uniformly dispersed throughout the tantalum carbide.

3. A method of making an alloy imporous at a magnification of 1500 diameters, which comprises uniformly dispersing substantially 11% by weight of nickel and 9% by weight of tungsten throughout substantially by weight of tantalum carbide while heating the powders of said nickel, tungsten and tantalum carbide in vacuo to a temperature below the melting point of any of the said constituents.

4. A sintered tantalum carbide alloy, having a greater actual density than the average density of its constituents, said alloy having a substantially aphanitic phase and a nickel-rich substance, resembling crystallites, of nickel and tungsten uniformly and intermittently dispersed throughout such phase, the nickel and tungsten which form said nickel-rich substance together constituting less than 25% by weight of the alloy, said alloy having been produced by sintering in vacuo and being characterized by its relatively great strength and hardness with respect to an alloyproduced from the same raw material by sintering in an inert atmosphere.

5. A sintered alloy for tools adapted to work steel without substantial cratering, such alloy consisting substantially of tantalum carbide and a nickel-rich substance, resembling crystallites, of nickel and tungsten intermittently and uniformly formed in situ throughout the alloy, said nickelrich substance constituting less than 25% by weight of the alloy, and said alloy having been produced by sintering in vacuoand being characterized by a greater actual density than the average density of its constituents and being further characterized by its relatively great strength and hardness with respect to an alloy produced from the same raw material by sintering in an inert atmosphere.

CLARENCE W. BALKE. 

